Most currencies presently in use today employ magnetic ink in the printing of at least a portion of the currency. The use of such ink enables certain portions of the currency to be machine readable. For this reason, magnetic ink is often used for printing of the currency serial numbers.
Apparatus is known for detecting the magnetic ink in a currency sample for determining its authenticity. Such apparatus, as presently available, suffers from a number of disadvantages. A primary disadvantage is that the orientation of the magnetic sensing head must be maintained within a predetermined, relatively narrow range to provide detection.
A second difficulty is that the apparatus must be switched on by a separate switch and then switched off after use to preserve the power of the battery which powers the apparatus. This is inconvenient in practice and often results in premature battery wear.